Stereo depth cameras are well-known and are often used to measure a distance from an object. One such measurement device includes a projector and a camera. In such a device, the projector projects a known pattern image on an object (e.g., a scene), and an image of the object upon which the image is projected is captured by one or more cameras. From the captured images, depth information may be determined. One technique for determining depth in such devices is through the use of triangulation. Thus, images of objects are captured and measurements are taken to determine depth information.
The camera(s) in such depth camera systems, may be complementary metal-oxide semiconductor (CMOS) sensor based cameras. One type of CMOS sensor based camera utilizes a global shutter, which exposes all pixels of the CMOS sensor at a single time, much like a typical film-based camera system. CMOS sensors with global shutters are both expensive and can experience delays in processing image data because all of the CMOS sensor pixels are exposed at once. Another type of CMOS sensor based camera utilizes a rolling shutter, which sequentially exposes rows of pixels of the CMOS sensor, from top to bottom of the CMOS sensor.
Regardless of what type of CMOS sensor is used for the camera(s) in a depth camera system, which attempts to capture a projection pattern generated by the system's projector to assist in the determination of depth information for a capture scene, the CMOS sensors are subject to noise. In this case, noise is any light in a scene that is not generated by the camera system's projector, but which is in the camera's wavelength of interest. Increased noise will require a stronger signal generated from the projected pattern to achieve the required accuracy of depth determination. In certain environments, such as outdoors, the problem of noise is exacerbated because of the amount of ambient light of different wavelengths, especially uniform background infrared illumination. Therefore, it may become difficult to determine depth information for a scene using projector based stereo depth imaging systems.